Monopole antenna



Dec. 31, 1968 R. L- TANNER E'TAL 3,4 9,873

MONOPOLE ANTENNA Filed Dec. 9, 1964 Y Sheet of 5 3:9" 4 //v VENTORS TO XMTR euyvvm POBEET 4. TANA/EE 76 74 .7 M06N$ a. ANDRL'AfEA/ 78 QA VK B. HAR/P/S A 7TORNEY R. L. TANNER ETAL 3,419,873

Dec. 31, 1968 MONOPOLE ANTENNA Sheet Filed Dec. 9, 19-64 TRANSMHTER 5 fr OM KJ 5 25 m W/J M A 50 R5 P. ENK waw w 0 v pmmw B TRANsMflTER .TANNER EIAL I 3,419,873

NTENNA Dec. 31, 1968 United States Patent ice 3,419,873 MONOPOLE ANTENNA Robert L. Tanner and Mogens G. Andreasen, Menlo Park, and Frank B. Harris and Edward M. Jones, Portola Valley, Calif., assignors, by mesne assignments, to Control Data Corporation, Minneapolis, Minn, a corporation of Delaware Filed Dec. 9, 1964, Ser. No. 417,074 2 Claims. (Cl. 343-847) ABSTRACT OF THE DISCLUSURE There is provided an arrangement for interconnecting the guy wires which support a monopole antenna having top load conductors, to provide an inductance which is connected for tuning the antenna. In addition, a novel ground current distribution system is provided which reduces the ground current resistance loss.

This invention relates to antennas of the type known as monopole antennas and more particularly to improvements therein.

A monopole antenna of the type presently being used usually comprises a vertical tower which is connected to a transmitter. Top loading conductors are connected to the top of the tower. These top loading conductors are usually supported in a manner so that they are radially extended from the tower. These conductors are used to increase the effective height and capacitance of the antenna. The tower is normally supported by a guy wire system. Typically, also, the guys are insulated from the tower and from guy anchors which are in the ground, by strain insulators.

In an application for patent entitled Monopole Antenna, by Robert L. Tanner, Ser. No. 225,815, filed Sept. 24, 1962, now Patent No. 3,253,279, which is assigned to a common assignee, there is described an improvement in monopole antennas wherein provision is made for interconnecting the guy wires with the transmitter and the radiator wires in a manner so that the guy wires operate as large inductive loops which are excited and which help to resonate or tune the antenna, and to provide additional radiation from a loop radiation mode which augments the radiation of the normal electric dipole radiation mode of the antenna. In one arrangement shown and described in that application, the tower is insulated from the top load conductors and the guy wires, so that no current flows through the tower and the tower is grounded. This arrangement has the advantages of eliminating the requirement for a base insulator for the tower, enables the tower itself to be at ground potential, and facilitates lightning protection. These benefits are accomplished at some penalty in antenna performance because the presence of the grounded tower reduces somewhat the effective height, the frequency bandwidth and radiation efiiciency of the antenna. However, there are circumstances in which the performance penalty paid for the convenience and advantages of the grounded tower cannot be justified technically or economically. Under these circumstances it would be advantageous to employ an antenna configuration which incorporates many advantages set forth in the previous application, but adds to the radiating system of top loads and loop guys of the antenna tower, insulated at its base.

There are also circumstances in which it may be desired to change the tuning of the antenna rapidly from one frequency to another. Under such circumstances, it may be easier and less expensive to effect the tuning by a more conventional tuning inductance located at the base of the tower rather than by the interconnection of the guy wires 3,419,873 Patented Dec. 31, 1968 to form multiple tuning inductances. It would be desirable, however, even when utilizing more conventional tuning methods, to utilize certain features of the antenna described in the above-stated application which result in the reduction of ground losses.

Accordingly, an object of the present invention is to provide a monopole antenna wherein, in addition to the top load conductors and guy wires being used for radiation, the antenna tower also is used for radiation, without detracting from the efiiciency of the antenna system.

Yet another object of the present invention is the provision of an improved and novel monopole antenna arrangement, achieving improved efiiciency for a given cost by effecting a reduction of ground losses.

Still another object of the present invention is the provision of a monopole antenna of the type described which has an extended bandwidth.

These and other objects of the invention are achieved in an arrangement of a monopole antenna wherein the guy wires, the tower, and the top load conductors are interconnected in a manner so that they all cooperate to perform the function of radiation. Further, a novel ground current distribution system is provided consisting of closed loop insulated conductors which reduce the ground current resistance loss.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a view in elevation of a monopole antenna which is constructed in accordance with this invention;

FIGURE 2 is a plan view of a monopole antenna in accordance with this invention;

FIGURES 3A, 3B and 3C are schematic representations of some other ways of interconnecting the radiating guy wires to vary the coarse tuning of an antenna;

FIGURE 4 is an arrangement illustrating how the monopole antenna, in accordance with this invention, may be connected to a ground conductor ring;

FIGURE 5 is a drawing illustrating a novel ground current distribution system and how a monopole antenna is connected thereto;

FIGURE 6 is a schematic drawing illustrating a ground current distribution system in accordance with this invention, illustrating ground current distribution; and

FIGURE 7 is a drawing illustrating said novel ground current distribution system and how an improved monopole antenna in accordance with this invention is con nected thereto.

Reference will now be made to FIGURES 1 and 2 which respectively show elevation and plan views of an antenna which is constructed in accordance with this invention. The tower of an antenna may be supported by three or more sets of guy wires usually spaced apart around the tower, and in addition there are a number of top load conductors extending from the top of the tower. In order to clarify the drawing of FIGURE 1, only two sets of guy wires are represented and only two top load conductors are shown. FIGURE 2, however, does show a plan view of a monopole antenna in accordance with this invention having a full complement of both guy Wires and radiating conductors.

An antenna tower It} in accordance with this invention is supported by an insulator 12 so that it is insulated from the ground 14. Assume, by way of illustration, that there are five guy wires in each of the two sets shown, respectively 16A, 16B, 16C, 16D, 16B and 18A, 18B,

18C, 18D and 18B. The guy wires 16B, 16C, 16D and 16E are connected to the tower at spaced points along its length through strain insulators 20B, 20C, 20D and 20E. The ground ends of the guy wires 16A through 16E are respectively connected to ground through strain insulators respectively 22A through 22E. The tower ends of the guy wires 16A, 18A are directly connected to the tower. Although the guy wires connected to the tower are shown in the figure as being the lowest among the five in each group, it will be made evident that other connection arrangements are possible.

Guy wires 18B through 18E have one of their ends connected to the tower at spaced points along the length thereof through strain insulators respectively 24B through 24E. The ground ends of the guy wires 18A through 18E are connected to the grounding point through strain insulators respectively 26A through 26E.

Two top load conductors are shown by way of example, respectively 28, 30. These have one end connected to the top of the tower to make a conductive connection therewith, similar to the connection made by the ends of the guy wires 16A, 18A. The other ends of the respective top load wires are connected by means of respective strain insulators 31, 32, to ground.

The transmitter 34 for the antenna has one output terminal 36 connected to the guy wire 16C at its lower end and the other output terminal 38 is connected to a ground current distribution system. A jumper connection 40 connects the upper end of the guy wire 16C to the upper end of the guy wire 16D. By upper ends of these guy wires is meant the ends which attach to the strain insulators 20C, 20D. A jumper 42 connects the lower end of the guy wire 16D to the lower end of the guy wire 16B. By lower ends of the guy Wires is meant the ends of the guy wires which are connected to the strain insulators respectively 22B, 22D.

The upper end of the guy wires 16B is then connected to a jumper 44 to the upper end of the guy wire 16E. The lower end of the guy wire 16E is connected by a jumper 46 to the lower end of the guy wire 16A. The upper end of the guy wire 16A is connected to the tower 10, and since the tower is conductive, current can flow therealong up to the top load conductors which are connected to the top of the tower and thence out through the top load conductors.

From the foregoing description, it should be clear that current will flow in the direction represented by the arrowheads shown in the guy wires and the arrows on the tower. That is, current will flow from the transmitter up guy wire 160, then along jumper 40 to guy wire 16D. It will then flow down guy wire 16D along jumper 42 up guy wire 16B. Current will then flow along jumper 44 to guy wire 16E. Current will then flow down guy wire 16E along jumper 46, up guy wire 16A, up the tower to the radiating conductors 28, 30. From the foregoing description, it should also be appreciated that the guy wires in the group 16 have been interconnected together to form a multiple radiating inductor. The tower also carries current in a direction so as to contribute to the radiation of the guy wires and the radiating conductors.

The guy wires in the group 18 are similarly interconnected by jumpers as the guy wires in the group 16, except that instead of the guy wire 16C having its lower end connected to the transmitter terminal 36, its lower end is connected to the ground current distribution system 64 by a connector 60. The structure of the ground current distribution system is explained in the description of FIG- URES 2 and 3. Thus, the current flow in the guy wires of the group 18 will be identical with that for the group 16, as indicated by the arrowheads. Jumper 50 is analogous to jumper 46, and connects the lower end of guy wire 18A to the lower end of guy wire 18E. Jumper 52 is analogous to jumper 44, and connects the upper end of guy wire 18E to the upper end of guy wire 188. Jumper 54 is analogous to jumper 42 and connects the lower end of guy wire 18B to the lower end of guy wire 18D. The upper end of guy wire 18D is connected by jumper 56 to the upper end of guy wire 18C. The lower end of guy wire 18C is connected to the current distribution system by conductor 60 as previously stated.

The resulting circuit is one having three branches connected in parallel. The first branch is the multi-turn loop inductor formed by guy wire group 16 which is connected to the transmitter. The second branch is the multi-turn loop inductor formed by guy wire group 18. The third branch consists of the capacitance formed by the antenna structure and ground to form an electrically resonant system with the other two branches. Current flows in guy wire group 18 in parallel with the current flowing in guy wire group 16 with the direction of current flow at a particular instant in the several conductors of each group being as indicated by the arrowheads shown in FIGURE 1. Energy losses in the system due to radiation, to resistive loss in the conductors comprising the antenna system, or resistive loss in the ground, are supplied by the transmitter which is connected in series with one of the inductors formed by suitable interconnection among the different members of the guy wire group.

FIGURE 2 illustrates a plan view of a typical monopole antenna in accordance with this invention. The guy wire sets 16, 18 and 62 support the tower 10. These sets are spaced around the tower 10'. By way of illustration, fifteen top load conductors of the type 28, 30 are shown distributed evenly around the tower.

FIGURES 3A, 3B and 3C each illustrate schematically with a single guy wire set some alternative arrangements for interconnecting the radiating guy wires in order to achieve coarse tuning of a monopole antenna. The electrical connections for each set of guy wires is difierent, yielding a number of discrete resonant frequencies. Fine tuning may be done, as shown in FIGURE 3B, by using a small inductor 69, or inductors, connected in series with the transmitter. Alternatively, fine tuning may be done, as shown in FIGURE BC, by using a small capacitor 71, or capacitors, connected in series with the transmitter.

In order to reduce the current density of the ground return current to the transmitter, ground connections may be made to a circular conductor in the manner taught in the previously-mentioned application to Robert L. Tanner, or connection may be made to one or more closed circular insulated cables 64, which are buried in the ground around the outer periphery of the region of the monopole antenna. Each insulated cable 64, as is seen in FIGURE 1, has a conducting wire core 64A surrounded by a dielectric insulating sheath 64B buried directly in the earth.

In order to equalize the current distribution in this circular buried insulated cable, distributing connections may be made thereto such as, by means of the conductors 68, 70, 72, which are shown in FIGURE 2. The conductor 68 connects to the insulated ground current distribution cable 64 on either side of the transmitter ground return connection, an equal distance, to insure that the current distribution in the conductor and therefore the displacement current in the ground is uniform. Similarly, conductors 70, 72 connect to the insulated cable 64 on either side of the connections to ground, made by way of jumpers, such as 60 shown in FIGURE 1, to equalize the distribution of current to the cable 64, and to maintain uniform displacement current distribution in the ground and return conductors. The displacement current enters the ground through the capacitance set up between the conductor 64A and ground.

If connections of the type represented by conductors 68, 70, 72 are insufiicient to insure good current distribution together with a reasonable current density, an arrangement as is shown in FIGURE 4 may be employed. This arrangement resembles a tree wherein the connection 74 to the transmitter or guy wire is divided into two further connections by means of a conductor 76,

each end of which is divided into still further connections by means of conductors 78, 80. Each one of the ends of the conductors 78, 80 are connected in parallel to ground current distribution cables 64, 65. By evenly spacing the points of connection between the ground terminal of the transmitter and/ or the guy wires, and the ground current distribution cables 64, 65, both the current distribution in the conductors is equalized, and the ground current density is reduced. The use of insulated conductors for the ground current distribution has the property that the insulating material of the cable is the dielectric of a capacitor of which the conductor is one electrode and ground is the other electrode. The capacitor thus established distributes the displacement current into the ground vequally all around the large circular ring at the periphery of the antenna, minimizing the ground current density and consequently the ground losses of the antenna.

As thus far described, the ground current distribution system comprises a conductive insulated ring or rings at the periphery of the base of the cone described by the monopole antenna with ground current emanating from this ring. In accordance with this invention, and as shown in FIGURES 5, 6 land 7, the conductive rings can also be arranged so that each ring supplies charge to an appropriate area under an antenna, the arrangement of the rings being such that the charge is supplied by essentially equal displacement current flowing radially both in and out from each ring.

FIGURE shows schematically how a ground current distribution system arrangement, in accordance with this invention, can be used with a conventional insulated tower monopole antenna system. The monopole antenna 80 is represented schematically. The transmitter 82 has one terminal connected to the base of the tower 84, above the insulator 86. The ground terminal of the transmitter is connected by means of typical branching conductors 88, 90, 92, insulated drop lines, such as 94, 96, 98, and insulated buried cross connected conductors such as 100, 101 to the respective concentrically disposed current distribution rings 102, 104, 106, which are buried in the ground. These current rings are represented by dotted lines. It will be appreciated that each one of these rings is an insulated cable, such as cable 64, previously described in connection with FIGURES 1, 2 and 4. The branching conductors 88, 90, 92 may be supported above the ground by means such as poles 108, 110, 112.

FIGURE 6 is a plan view of the ground under the antenna showing the area in which substantial surface charge must be supplied to the surface of the ground to terminate the electric field lines originating on charges of opposite sign carried by the top load conductor system of the antenna. It will be recognized by those skilled in the art that the charge on the ground and on the top loading system of the antenna must be interchanged twice each cycle of the radio frequency voltage applied to the antenna by the transmitter, and that this interchange is aflected by the flow of current in the ground and on the antenna conductors. Dotted lines 102, 104, 106 are the same insulated ground distribution conductors shown in FIGURE 5. Hatched areas 114, 116, 118 are the areas to which charge is supplied by the respectiveinsulated ground distribution conductors. Arrows 120 represent displacement current flowing radially inward from conductor 104 to supply charge to the inner portion of area 116, while arrows 122 represent displacement current flowing radially outward to supply charge to the outer portion of area 116.

FIGURE 7 shows schematically how a ground current distribution system arrangement in accordance with this invention can be used with a monopole antenna system, such as has been described herein. The monopole antenna 124 is represented schematically. The transmitter 126 has one output terminal connected to the lower end of one of the guys. The other transmitter output terminal is connected to a branching conductor 130, which in turn is connected to buried cross-connecting conductors 132,

6 134. These connect between the buried current distribution rings 136, 138, 140.

The lower end of any one of the guys, such as guy 142, which is to be connected to ground is connected instead to a branching conductor .144, which in turn is connected to buried cross-connecting conductors 146, 148. These connect between the buried current distribution rings 136, 138, 140. The branching conductors are supported above the ground by any suitable insulating means, such as poles, not shown.

It should be apparent from the foregoing that the function of the branching conductors including the cross-connecting conductors is to provide an even current distribution arrangement for the current distribution rings which in turn serve to reduce the ground current density in accordance with the principle illustrated in FIGURE 6, thereby cutting down ground resistance and antenna loss due to this factor.

While only three current distributing conductor rings are shown in the foregoing application, this is shown merely by way of illustration. More or less of these rings may be used as desired. However, as a general rule for selecting the number of rings which should be used, as well as their location, in the design of a monopole antenna, it is sufficient to plot a curve of the charge density anticipated on the ground surface under the antenna as a function of radius. This is a symmetrical, somewhat bellshaped curve. The area under this curve, at either side of the center may 'be divided into equal area segments and the ground ring conductors are placed so (that each one is at the center of an equal area segment.

There has accordingly been described and shown herein a novel, useful and unique arrangement for an antenna of the monopole type having a construction and excitation such that the antnna bandwidth is improved and the usual tuning helix is eliminated by suitably interconnecting the guy wires together with the antenna tower and top loading conductors to perform the required tuning function. The antenna is thereby made an essentially self-resonant structure in which the interconnected guys not only replace the tuning helix but also augment antenna radiation by acting as radiating loops. In addition, the ground current distribution arrangement as described herein serves to minimize ground losses for a given investment in the ground system by minimizing ground current density.

What is claimed is:

1. A top loaded antenna having a conductive tower with one end insulatingly supported above the earth, means for holding said tower vertical including a plurality of sets of guy wires spaced around said antenna tower, each set of guy wires including a plurality of guy wires which are attached to said tower at spaced points along the length thereof, a plurality of top loading conductors conductively connected to the top of said tower and extending radially outward therefrom, a plurality of insulating means for connecting one end of each of the guy wires in a set insulatingly to ground, a' second plurality of insulating means for connecting the other ends of all of the guy wires in each set insulatingly to said tower at spaced points therealon-g, means for conductively connecting the other end of one of the guy wires in each set to said tower, a separate connector means for each set of guy wires for interconnecting the guy wires in each set to form an inductance having two ends, one of which is the end of said one of said guy wires which is connected to said antenna tower, a ground current distribution system, means for connecting each of the other ends of the inductances formed by two of said guy wire sets to said ground current distribution system, said means for each of said inductance including:

a first elongated conductor having two ends and a center, means connecting said first elongated conductor center to said other end of said inductance, said ground current distribution system includes a closed loop insulated conductor underneath said antenna, and means connecting both ends of said first elongated conductor to spaced points along said insulated conductor including two further elongated conductors having centers and two ends, means connecting the two ends of said first elongated conductor to the centers of said second two elongated conductors and means, connecting said two ends of said second elongated conductors to spaced points along said insulated conductor cable and means for applying excitation between said ground current distribution system and the other end of the inductance formed by the third of said guy Wire sets. 2. In a top loaded antenna as recited in claim 1 wherein said means connecting for applying excitation between the other end of one of said inductances and said grounding means includes a variable impedance for enabling the fine tuning of said antenna.

References Cited UNITED STATES PATENTS Alexanderson 343849X Dow 343874X Koch 343849 Willoughby 343874X Seeley 343-874 X Tanner 343849 Reuthe 343725 Tanner 343847X HERMAN KARL SAALBACH, Primary Examiner. 15 W. H. PUNTER, Assistant Examiner.

U.S. C1.X.R. 

